German Patent Application No. DE 2061422 A1 discloses a mixing machine. This mixing machine comprises a stationary mixing table and a number of rollers configured for interactive operation with the mixing table. Each roller rotates about a separate roller shaft, which is connected to a vertical shaft via a hinged connection. The center of rotation for the hinged connection allows a free circular movement of the roller in upward and downward direction in a plane comprising the centerline of the roller shaft. The center of rotation of the hinged connection is located under the horizontal centerline of the roller shaft. In this way the centrifugal force, which during the operation of the mill acts upon the roller, will produce a turning moment around the hinge and hence a force directed downward against the grinding table. This mixing machine is used in foundries for mixing water, sand and binding materials to a viscous mass of molding sand. The mixing table is formed with walls so as to form a bowl to prevent water to escape from the mixing process. This process is not continuous since the mixing machine has to be stopped and the viscous mass of finished molding sand has to be removed before a new batch of water, sand and binding materials can be fed to the machine. Such stops causing considerable down-time of the machine are expensive in terms of time and furthermore it is a labour-intensive task to remove the finished molding sand.